1. Field of the Invention
This invention relates to a wrapping machine which is equipped with a folding and opening unit for drawing a wide wrapping material of film, synthetic resin laminate or the like from a roll, continuously folding the wrapping material longitudinally about its center line and, at the same time, opening the folded wrapping material, and then conveying the resulting wrapping material to a subsequent station.
2. Description of the Related Art
Wrapping machines most similar to the continuous wrapping machine of the type described above are disclosed in, for example, Japanese Patent Publication No. SHO 60-2914, Japanese Patent Laid-Open Publication No. HEI 4-102508 and Japanese Patent Laid-Open Publication No. HEI 4-102509. FIG. 10 of the accompanying drawings illustrates the principle of a folding unit of the individual prior art wrapping machine for continuously folding a wrapping material such as of film (hereinafter called the film), which is to be continuously supplied from a roll, longitudinally about its center line.
The known folding unit comprises a first guide 100 having a horizontal guide section 101, which is situated above a rotatable horizontal film roll FR in parallel to its roll shaft and has a length about a half of the film F, and an inclined guide section 102, which is connected to one end of the horizontal guide section 101 and is inclined downwardly by about 45.degree., and a second guide 200 having at least an inclined guide section 201, which is situated close to the front side in a supplying direction of the first guide 100 and is inclined downwardly by about 45.degree. from the upper end of the inclined guide section 102 to below the free end of the horizontal guide section 101, and a non-illustrated guide roller situated under the inclined guide section 201 of the second guide 200 in parallel to the roll shaft and having a length at least about a half of the width of the wrapping material.
In the horizontal guide section 101 and the inclined guide section 102 of the first guide 100, one half of the wide film F to be drawn vertically upwardly from the film roll FR is turned at an angle of 180.degree. downwardly, while the other half width of film F is turned downwardly at an angle of 45.degree. and again turned vertically downwardly from inside to outside around the inclined guide section 201 of the second guide 200 situated upstream of and close to the horizontal guide section 101 of the first guide 100. While the film F is moved forwardly along a longitudinal path, it is folded longitudinally about its center line; one half width of the film F is directed downwardly via the horizontal guide section 101 of the first guide 100, and the other half width of the film F is directed forwardly via the inclined guide section 201 of the second guide 200, whereupon the folded film F is then turned in the horizontal direction as guided by the non-illustrated guide roller, and is transferred to the next station.
In the prior art wrapping machine, the folded film F-1, F-2 is turned by a right angle while it is opened by a non-illustrated opening device of the next station so as to have a generally horizontal U-shape cross section. Into this opening of the film turned by a right angle, articles to be wrapped are conveyed one after another at predetermined intervals by a non-illustrated belt conveyer inserted longitudinally (as indicated by an arrow Y) of the wrapping machine. Then the folded film F is fused and cut at two side openings around the article by a non-illustrated L-type sealer.
However, in the wrapping machine disclosed in the above-mentioned prior art references as well as any other continuous wrapping machine in this kind, the film folding device is connected with a film opening device for opening the folded film. With this structure, when the folded film is opened by drawing, static electricity would occur due to friction during taking up of the film, and blockage would occur due to adhesion of films. As a result, the prior art continuous wrapping machine requires an increased number of component devices which not only needs an increased space for installation of all the devices but also gives large influence to the cost of installation, operation management, etc.